The objective of this independent postdoctoral fellowship award (F32) is to support the candidate's training goals to gain knowledge on substance use and psychiatric outcomes, expertise in genetic epidemiological and gene-finding methods, and further develop the skills needed for an academic research career. To achieve these training goals, the candidate will use genetically informed designs to characterize the associations between externalizing behavior and relationship factors. Numerous studies document associations among externalizing behavior (e.g., alcohol and illicit drug abuse and dependence and antisocial behavior), marital status, and romantic relationship dysfunction. Externalizing behavior and relationship traits are both under genetic influence; still, little is known about their associations from a genetic perspective. Characterizing these associations is important in view of growing evidence that genetic predispositions and environmental risk factors are not independent of one another. With respect to the present project, for example, behavioral disinhibition (i.e., the highly heritable factor shared among externalizing behaviors) also compromises the interpersonal processes (e.g., conflict resolution, trust, and commitment) that are central to the formation and maintenance of harmonious romantic relationships. Two central hypotheses guide this work. First, it is expected that marital status and relationship dysfunction will have a common genetic basis with externalizing behavior. Second, it is expected that, after accounting for gene-environment correlation, marital status and relationship dysfunction will moderate genetic influences on externalizing behavior. The first part of this project will use genetic epidemiological (i.e., twin) methods to examine whether externalizing behavior and romantic relationship factors share latent genetic influences and whether romantic relationship factors moderate latent genetic influences on externalizing behavior. The second part of this project will use gene-finding methods to examine whether externalizing behavior and relationship factors share measured genetic influences, and whether relationship factors moderate measured genetic influences on externalizing behavior. Thus, this work uses complementary genetically-informed methods (twin studies and gene identification methods) to determine the extent to which genetic and/or environmental influences toward externalizing behavior also influence one's propensity to marry, divorce, or have a dysfunctional relationship, and whether relationship factors moderate genetic influences on externalizing behavior. This work contributes to a central goal of psychiatric research, which is to understand how salient environmental factors, such as marital status and relationship dysfunction, come together with genetic predispositions to predict the onset and course of disorders.